Muffler



P. G. PEIK Sept. 17, 1935.

MUFFLER Filed Oct. 5l, 1932 2 Sheets-Sheet l Flai PH UL E' PEIK Patented Sept. 17, 1935 UNITED STATES MUFFLER Paul G. Peik, Chicago, Ill., assignor to The Halsey W. Taylor Company, Warren, Ohio, a corporation of Ohio Application October 31, 1932, Serial No. 640,557

2 Claims.

Another object of the invention is to provide a muffler of highest known efficiency at a cost materially lower than the cost of mulers of comparable efliciency The following brief reference to the behavior of sound waves and the nature of sound impulses in the exhaust stream of internal combustion engines will serve to show how the above objects are attained andto bring out the salient features yof this invention.

Fundamentally all sound deadening is due to resonance action. The highest efficiency of sound deadening-that is, elimination of any sound wave in one cycle,-is attained only by providing a separate chamber tuned exactly to the length of that wave. This method is not feasible in a muffler, due to the multiplicity of sound waves in the exhaust stream,.and the constant variation of their frequency due to the acceleration and deceleration of the engine. While each individual air space in sound absorbing material employed in muillers of the so-called acoustic type, is far too small to have an efficient sound deadening action in one cycle, acoustic mutllers are nevertheless very efficient in deadening high frequencies of sound due to the multiplicity of air spaces and the high rate of oscillation of the high frequencies. rlhus the so-called acoustic mulers are extremely efficient in eliminating the high frequencies, but (for reasons which are explained later) are so ineicient in their action on the low frequencies that such mufflers must be made in a considerable length to obtain the necessary elimination of the low sound frequencies,

- so long in fact that it is common practice to make them in two units so that they can be mounted between the re-inforcing members of the modern automobile chassis.

The lower eciency of acoustic muiilers in eliminating the low frequencies of sound is, of

5 course, due to lthe low rate of oscillation of the low range of sound frequencies. These are more mulers require a long series of such chambers, resulting in a muiller of extreme length. Obviously the relative inefficiency of these resonance chambers on the high frequenciesA is due to the `fact that the chambers are relatively few in number 5 and not a multiplicity of spaces or cells to multiply the effect of the oscillations, as is the case in acoustic material- Before stating how the objects of this invention are accomplished it is necessary to refer briefly 10 to another characteristic of the sound impulses in` thev exhaust stream of internal-combustion engines; namely, in the entire acceleration range there is a relatively small number of low periods of frequency of sufficient amplitude or intensity, 15 as to be ineiectively absorbed by acoustic material. The rest of the frequencies in the low range are of a much weaker intensity so that they f are sufficiently eliminated by acoustic material despite its characteristic ineiciency in deadening A20 sounds of low frequency.

Thus the objects of the invention are accomplished by (l) combining the acoustic and resonator principles providing the most efficient deadeningV of both the high and and low ranges of 25 sound frequencies (2) by employing a new and useful form of resonance chamber which (a) produces resonance so that the loud period or band of low frequency may be tuned out decisively by one chamber and (b) which can be employed in 30 a muiiler having -an overall length only a fraction of the length of any of the resonance chambers required to decisively tune out the loud period of low frequency.

The objects of this invention and the man- 35 ner in which these objects are accomplished will become apparent as the following description progresses and is considered in conjunction with the accompanying drawings wherein:

Figure 1 is a longitudinal sectional View through 40 the muffler accordingl to the invention, the section being taken on line l-I of Figure 2;

Figure 2 is a cross sectional view of the mufiler taken on line 2-2 of Figure 1;

Figures 3 and 4 are cross-sectional views of the 45 muillertaken on line 3-3 and line 4-4 respectively of Figure 1";

Figure 5 is a longitudinal sectional view throug the muiller taken on line 5-5 of Figure l;

Figure 6 is a cross sectional viewon line 6 6 50 Figures 7 through 12 show a modified form o the murder, provided with three separating fins, to increase the number of resonator chambers employed. Thus, Figure 7 is a longitudinal sec- 65 tional view through the modified muiler taken on line I--l of Figure 8 and Figure 8 is a cross sectional view on line 8--8 of Figure '7. Figures 9, 10 and 11 are cross sectional views taken on line 99, IU-III and II--II respectively of Figure 7. Figure 12 is a perspective view of the inner portion of the muffler with the fins attached thereto to show the difference in length of the fins.

Referring more particularly to the structure disclosed in Figures 1 through 7 of the drawings the muffler I comprises outer and inner sheet metal concentrically arranged cylinders 2 and 3. These cylinders are connected at opposite ends in any suitable manner, as by welding, to the front and rear end walls 4 and 5 respectively, thus forming an annular resonating space 6 between the two cylinders. These end walls are formed with inlet and outlet extensions 1 and 8 communicating with the inlet and outlet openings 9 and I0 respectively. A third shell or container II of octagonal or other multi-sided form is firmly enclosedwithin the inner cylinder 3, and this shell encloses a round sleeve or pipe I2 in axial alinement with the respective inlet and outlet openings 9 and Ill, and extending from inlet opening I3 in inner end wall Il of shell II to and through outlet opening I5 in the outer end wall I6 thereof. The outer end of pipe I2 terminates well within the outlet extension 8, while the inner end is flush with the wall of inlet opening I3. Both members II and I2 are made of perforated sheet metal, and the interior of the former member surrounding the pipe I2 is packed with any sound absorbing, fire proof material II such as expanded micaceous material, slag wool, steel wool, etc.

'I'he end walls I4 and I6 of shell II are spaced a small distance from the end walls l and 5 common to both cylinders 2 and 3, thus forming chambers I8 and I9 at the front and rear ends of the muffler respectively. The space inside of pipe I2 communicates with chamber I8 and constitutes an unobstructed main passage for the exhaust gas. This passage communicates through perforations in pipe I2 with the expansion chamber or space 20 within octagonal shaped shell II, which chamber is packed with sound absorbing and dlssipating material and extends between the end walls Il and I6 as previously stated. Expansion chamber 20 in turn communicates through perforations in the wall of shell II with the spaces or passages 2| between cylinder 3 and shell I I, which spaces are continuous from end to end of chamber 20 and are constantly subjected to the full suction action of ex,- haust gases, blowing through and expelled from discharge end of pipe I2. These expelled gases draw the exhaust gases from spaces 2| with a smooth venturi-like action due to the extension of pipe I2 into outlet extension I. It will be noted that the passages 2l are in communication with chamber I0 as well as with chamber I9 and that in consequence an extremely free flow of gas is obtained through the muffler, thus insuring the desirably low back pressure.

Due to the functional factors of the venturi, this structure provides an unusually high degree of mullling efficiency. It is thus possible to obtain any desired difference in the rate of flow between the main gas stream I2 and auxiliary gas streams 2I. This staggering of the gas streams greatly facilitates the efficient expansion of high gasimpulse peaks of main passage I2 into the low areas of passages 2l, and vice versa. It is likewise possible to increase the gas flow capacity of this structure to an unusual degree, without the necessity of correspondingly increasing the diameter of the muffler or the volume of acoustic material, and at the same time avoid over rifiling or turbulence in the gas streams with the resultant loss of mutlling efficiency. These two factors are responsible for the unusually high degree of acoustic sound absorbtion within an extremely small diameter.

Up to this point I have described only the socalled acoustic action of the muffler, which action as previously explained is more effective on high sound frequencies than on the low, whereas the low frequencies are more readily mullled or silenced by a resonating action. Good muflling of both high and low frequencies has heretofore only been obtained by employing relatively long muillers which are difficult to mount, costly to manufacture, and due to their length stand in the way of the easy and economical solution of other chassis problems, such as reinforcing cross members and proper mounting of other accessories, etc. In order to obtain the desired resonator effect in combination with the acoustic action just described without the necessity of greatly increasing the length of the muffler of the present invention, the space between shells 2 and 3 is subdivided by fins 22, whereby an elongated reversed or U-shaped resonator chamber 23 of substantial length is formed. Chamber 23, which may be adapted to silence the loudest period of the loud periods of low sound frequencies, is approximately twice the length of the outer cylinder 2 and consequently is double the length of the muiller as a Whole, one-half of the length of chamber 23 being formed by the upper half cir cular space between cylinders 2 and 3, and the lother half by the corresponding lower half circular space. The fins 22 are shorter than the muiller to afford free communication between the two halves of chamber 23. A series of openings 24, in the inner end portion of cylinder 3 extending from end wall I4 of shell II to end wall I of the muiller provide direct communication between chamber I8 and one end only of resonance chamber 23. It should be noted that these openings are located only in one-half of the periphery of cylinder 3. This series of reversing sections in the resonance chamber makes it possible to decisively tune out the low frequency in a muiller of simple construction and extremely short length. The present structure makes it possible to materially amplify the tuning out of the one extremely loud period of low frequency present g inthe acceleration range of most motors.

In practice it has in many instances merely been necessary to make the total length of the resonator chamber 23 (and consequently its tuning) such as to decisively tune out this loudest period of low frequency without the necessity of any accurate tuning of other loud resonance periods in the low range to obtain a degree of muilling efficiency equal to that of so-called acoustic mufflers and resonator muillers two times as long as the muiller in question.

For internal-combustion engines having an unusually complex combinationv of distinct loud perlods of low frequencies the number of resonator chambers of the muffler is preferably increased. This can be effected by increasing the number of fins 22 subdividing the space between shells 2 and 3. A muffler provided with a larger number of resonance chambers is shown in Figures 7 to 12 of the drawings.

The structure disclosed in these figures closely resembles the muiller shown in Figures 1 through 6 with the exception that the space between shells 2 and 3 is subdivided by a n 25 which is shortei` than the length of the muiiier and by the two fins 26 extending over the entire length of the muiiier. This arrangement provides resonance chambers similar to long re` verse bend chamber 23 and the other shorter resonance chambers referred to above, and an additional resonance chamber 21 extending between ns 26. Chamber 21 communicates through holes 28 in the. wall of cylinder 3 with chamber I8, the latter being of slightly greater depth than chamber I8, previously described to permit proper location of the holes or openings 24 and 28 with respect to their resonance chambers.

From the foregoing it will be seen that by employing any number of resonance chambers or any number of reversing sections per chamber or both, muiliers according to this invention can be built which combine the highest degree of muffling eiliciency known in the art yet having an overall length which may be any desired fraction of the length of resonance chambers required for effective elimination of the loud periods in the low range of frequencies. Furthermore these results are obtained without any loss of the low back pressure so essential to the most eilicient engine performance.

Having thus described this invention:

-What I claimis:

1. A muiiler for silencing the exhaust noise of internal combustion engines embodying an outer shell closed at opposite ends by front and rear end Walls having inlet and outlet openings, an inner shell axially aligned with said first shell and arranged within said rst shell abutting said end walls, a perforated tube Within said inner shell in axial alignment with the inlet and outlet open 5 ings of said outer shell, and iins of different length attached to the outside surface of said inner shell parallel to the longitudinal axis thereof and connecting with the inner wall of said outer shell, said iins subdividing the annular space between 10 said outer and inner shell into parallel chambers communicating with the interior of said inner shell and forming a doubled back resonator chamber of approximately double the length of said muiler and coextensive therewith. 15 2. A muiiier for silencing the exhaust noise of internal combustion engines, embodying an outer shell closed at opposite ends by front and rear end walls having inlet and outlet openings, an inner shell within said rst shell abutting said 20 end walls, a perforated tube within said inner shell in axial alignment with the inlet and outlet openings of said outer shell, two tins equal in length to said inner shell arranged between said outer and inner shell parallel to the longitudinal 25 axis thereof for subdividing the annular space between said outer and inner shell into parallel resonator chambers communicating with said inner shell, a shorter iin arranged between said two iinsadapted to subdivide one of said cham- 30 bers into parallel communicating halves and form a doubled back resonance chamber having a length substantially greater than the said muiller.

PAUL G. PEIK. 

